An "engagement letter" was sent to Cuomo's staff last week, the comptroller's spokesman said.

This is the first audit of the attorney general's office to be performed since DiNapoli was named comptroller in 2007.

The two state watchdogs have experienced a few bumps in their relations in recent months. The attorney general's office is working on a multi-year investigation into abuses of the state pension fund during the tenure of Comptroller Alan Hevesi, a probe which has resulted in many high-profile indictments and guilty pleas.

The comptroller is the sole trustee of the $126 billion Common Retirement Fund. In October, Cuomo and several state legislators proposed replacing the centralized power with a 13-member board including the comptroller and appointees of the governor, the attorney general and legislative leaders.

Although DiNapoli has instituted many of the pension reforms favored by Cuomo, the comptroller is concerned about the constitutionality of eliminating the sole trustee model.

The audit begins as both Democrats prepare for the 2010 elections. Although Cuomo has not yet declared his intentions, he is perceived as a likely gubernatorial candidate. DiNapoli, a former assemblyman, has announced his intention to seek his first full term.

DiNapoli spokesman Dennis Tompkins dismissed the notion that the timing of the audit was due to anything other than the Comptroller's obligation to conduct its examinations across state government.

"There is no ulterior motive," Tompkins said. " ... This is what we do."

"We've received the letter and we're reviewing it," said John Milgrim, Cuomo's spokesman.

The Civil Recovery Bureau's various units includes the Oil Spills Unit. The comptroller's office oversees the Oil Spill Fund, which pays for the cost of cleaning up spills partly by collecting penalties from petroleum spillers. The Civil Recovery Unit acts as the comptroller's attorney in collection actions involving the fund.

Earlier this year, DiNapoli proposed legislation to give the state additional tools to go after deadbeat polluters. That move coincided with a Times Union investigation that found that many spillers have gone decades without settling their fines, leaving the state with almost $200 million in environmental IOUs.